Aromatic polyol end-capped unsaturated polyetherester resins and resin compositions containing the same having improved chemical and/or water resistance

ABSTRACT

Unsaturated polyetherester resins, and processes for making them, are described which are useful for making curable thermoset resin compositions, intermediates for curable thermoset resin compositions, fiber-reinforced polymer composites, intermediates for making skin laminates for gel coated fiber-reinforced composites and gel coated polymer laminates. The unsaturated polyetherester resins are obtainable by reacting at least one acid-terminated unsaturated polyetherester resin with at least one aromatic polyol having at least one non-primary hydroxy group to produce an unsaturated polyetherester resin at least partially end-capped with an aromatic polyol. The described processes, compositions, methods and uses improve the chemical and/or water resistance of resin compositions, particularly composite materials having a gel coat. That improvement has special significance in outdoor and marine applications, bathtubs and shower stalls, and environments exposed to chemicals such as industrial and commercial applications.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. patent application Ser. No.09/232,989, filed Jan. 19, 1999, now U.S. Pat. No. 6,211,305, issuedApr. 3, 2001, which claims the benefit of U.S. Provisional ApplicationNo. 60/071,951, filed Jan. 20, 1998.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention pertains to the field of polymer resins, curablethermoset resins, resin systems which include curable thermoset resins,composite materials and skin laminates for composite materials, andprocesses and intermediates for making the same.

2. Description of Related Art

Known gel coated fiber-reinforced polymers are subject to blistering ifimmersed in water or solvents for a prolonged period of time unlessspecial measures are taken to prevent this phenomenon. Blisters areraised by localized swelling of the gel coated laminate due to diffusionof water into the composite and the presence of water-solubleconstituents within the laminate. The blisters not only effect theexternal appearance of the gel coated fiber-reinforced polymer article,but also eventually lead to reduced composite strength.

Several methods have been proposed to reduce blistering in gel coatedcomposite materials. U.S. Pat. No. 4,724,173 describes using a permeablegel coat to allow the osmotically active molecules to diffuse from theosmotic centers through the gel coat at a defined transport rate wherebythe osmotic pressure of the osmotic centers is reduced so as to reduceblistering. U.S. Pat. No. 4,477,325 describes a method of manufacturinga skin barrier which has improved water resistance to protect thecomposite material from hydrolysis. U.S. Pat. Nos. 4,480,077 and4,525,544 describe vinyl ester resin compositions which may be used inthe laminate construction to impart greater resistance to waterpermeation and U.S. Pat. No. 4,959,259 describes a bisphenolic polyesterresin composition which may also be used to impart greater waterpermeation resistance.

The latter technique, using a laminate resin having greater corrosionand/or water resistance, is the most common technique used by thecomposite industry to reduce blistering. Those resins are typicallyvinyl ester resins or isophthalic polyester resins. Not only is thattechnique not always completely successful, it also increases theoverall expense of the composite material and/or reduces the flexibilityin choosing the laminating resin for other desired properties.

For these and other reasons, further improvements in the ability toprevent blistering are desired. These improvements have specialsignificance in outdoor and marine applications, bathtubs and showerstalls and environments exposed to chemicals, such as industrial andcommercial applications. These and other objectives are achieved by thepresent invention.

SUMMARY OF THE INVENTION

One aspect of this invention is a process for making unsaturatedpolyetherester resins that are useful for making curable thermoset resincompositions comprising reacting at least one acid-terminatedunsaturated polyetherester resin with at least one aromatic polyolhaving at least one non-primary hydroxy group to produce an unsaturatedpolyetherester resin at least partially end-capped with an aromaticpolyol. The aromatic polyol end-capped unsaturated polyetherester resinsobtainable by that process are also part of this invention.

Another aspect of this invention is curable thermoset resin compositionsuseful for imparting water and/or solvent resistance to gel coatedfiber-reinforced polymers comprising:

(A) At least 5 wt. % of at least one aromatic polyol end-cappedunsaturated polyetherester resin according to this invention;

(B) At least one unsaturated polyester resin having a number averagemolecular weight to the average number of double bonds per polymermolecule in the range from about 200 to about 400, in an amount suchthat the weight ratio of polyester resin (B) to polyetherester resin (A)is in the range from about 10:90 to about 90:10;

(C) About 10 to about 70 wt. % of at least one vinyl monomer; and

(D) At least one curing agent, and intermediates for making such curablethermoset resin compositions comprising all the components of thecurable thermoset resin composition except the at least one curing agent(D).

Two more aspects of this invention are fiber-reinforced polymercomposites obtainable by combining the curable thermoset resincomposition according to this invention with reinforcing fiber andcuring the curable thermoset resin composition and gel coatedfiber-reinforced polymers comprising such fiber-reinforced compositionsand a gel coat.

Yet another aspect of this invention is intermediates for making skinlaminates for gel-coated fiber-reinforced composites, the intermediatescomprising reinforcing fibers and the curable thermoset resincomposition according to this invention in the form of a sheet.

A further aspect of this invention is gel coated polymer laminatescomprising at least one fiber-reinforced polymer layer, at least one gelcoat layer, and at least one thermoset resin layer interposed betweenthe at least one fiber-reinforced polymer layer and the at least one gelcoat layer, wherein the at least one thermoset resin layer is obtainableby applying the curable thermoset resin composition or the skin laminateintermediate according to this invention as a barrier layer between thegel coat layer and the fiber-reinforced polymer layer and curing thecurable thermoset resin composition.

Two further aspects of this invention are methods for making a curablethermoset resin composition comprising combining:

(A) At least 5 wt. % of at least one unsaturated polyetherester resinaccording to this invention;

(B) At least one unsaturated polyester resin having a number averagemolecular weight to the average number of double bonds per polymermolecule in the range from about 200 to about 400, in an amount suchthat the weight ratio of polyester resin (B) to polyetherester resin (A)is in the range from about 10:90 to about 90:10;

(C) About 10 to about 70 wt. % of at least one vinyl monomer; and

(D) At least one curing agent.

Two further aspects of this invention are methods for reducingblistering of a gel coated fiber-reinforced polymer comprising:

(1) Applying at least one layer of the curable thermoset resincomposition or the skin laminate intermediate of this invention betweena gel coat layer and a fiber-reinforced polymer layer and

(2) Curing the curable thermoset resin composition, and articlesobtainable by such methods.

The invention is described in further detail below.

DETAILED DESCRIPTION OF THE INVENTION

Definitions

The term “unsaturated polyetherester resin” means polymer resins ofintermediate molecular weight that contain ethylenic unsaturationavailable for free-radical polymerization with a vinyl monomer,recurring ester units, and recurring polyether blocks. The polyetherblocks have repeat units of oxyalkylene groups (—O—alkylene-). They havecarboxylic acid end groups which react with at least one of theend-capping compounds.

The terms “hydrocarbyl”, “hydrocarbylene” and “hydrocarbylidene” eachrefer to a moiety made up of carbon and hydrogen atoms, and optionallyup to 10 percent of the total number of atoms in this moiety of othercovalently bonded atoms (i.e., covalently bonded hetero atoms, such asatoms of oxygen, sulfur, etc.). The moiety may, for example, containoxygen and/or sulfur atoms as ether or ester linkages. The term“hydrocarbyl” refers to such a moiety with a valence of one, and both“hydrocarbylene” and “hydrocarbylidene” refer to such a moiety having avalence of two. The term “hydrocarbylidene” refers to such a moiety inwhich both valences (i.e., both bonds to the remainder of the moleculeto which it is bonded) are on the same carbon atom. When these terms arepreceded by the term “predominantly” such as “predominantlyhydrocarbylene”, that indicates that the moiety may have up to, but notincluding, 50 percent based on the total number atoms in the moiety ofthe other covalently bonded atoms described above.

Examples of hydrocarbyl, hydrocarbylene and hydrocarbylidene(cumulatively referred to herein as “hydrocarb(yl/ylene/ylidene”) groupsinclude, but are not limited to, aliphatic groups, such as straight andbranched alkyl groups, having up to 12, more preferably up to 8, andeven more preferably up to 4 carbon atoms and a minimum of 1, morepreferably at least 2, carbon atoms, such as an ethylene, a propylene ora butylene group, preferably a propylene group; the aforementionedaliphatic groups having one or more pendant hydrocarbyl groups,including aromatic groups as well as aliphatic groups; cyclo-aliphaticgroups having from 5 to 7 carbon atoms; heterocyclic groups having from5 to 7 ring atoms in which at least half the atoms in the ring arecarbon atoms and the hetero atoms may be selected from any of theaforementioned hetero atoms; aromatic groups; and polymers comprisingthese hydrocarbyl groups interrupted by hetero atoms or hetero groups,such as ether and/or ester groups, preferably ether groups. A“nonaromatic hydro-carb(yl/ylene/ylidene)” group is one which does notcontain any aromatic groups. An “aromatic group” is any covalentlybonded group of atoms in which the majority of atoms are members of atleast one aromatic ring. The aromatic group preferably has up to 3, morepreferably up to 1, aromatic ring(s) and preferably at least 80, morepreferably at least 90, percent of the atoms in the aromatic group aremembers of an aromatic ring. Examples include benzene, naphthalene,etc., rings, which may optionally have substituents such as hydrocarbylgroups, functional groups containing hetero atoms, and hetero atoms, andsuch rings fused with each other or linked to each other directly orindirectly via covalent bonds. When the aromatic group is a bridginggroup between two or more parts of the same molecule, each bond to thearomatic group is preferably attached directly to an atom which is amember of an aromatic ring of the aromatic group.

An “aromatic polyol” is an aromatic group having at least twononphenolic hydroxy groups. Nonphenolic hydroxy groups are hydroxygroups that are not directly bonded to an aromatic ring, but areindirectly bonded to an aromatic ring via an atom or group of atoms thatare not members of an aromatic ring. The atom or group of atoms arepreferably a predominantly hydrocarbylene or hydrocarbylidene group.Aromatic polyols useful in this invention are described in more detailunder the Detailed Description of the Invention.

A “nonprimary hydroxy group” is a hydroxy group attached to a carbonatom which has more than one carbon atom bonded covalently directly toit, but which is not an aromatic ring member. A “secondary hydroxygroup” is a hydroxy group attached to a secondary carbon atom, which isa carbon atom that has two carbon atoms bonded covalently directly to itbut which is not an aromatic ring member. A “tertiary hydroxy group” isa hydroxy group attached to a tertiary carbon atom, which is a carbonatom that has three carbon atoms bonded covalently directly to it butwhich is not an aromatic ring member.

An ether linkage is a moiety of the formula —O— or —S—. An ester linkageis a moiety of the formula —C(O)O— or —O(O)C—, or the correspondingmoieties in which sulfur atoms are substituted for one or both oxygenatoms.

The terms “curing” and “cured” refer to the formation of a substantiallyirreversible three-dimensional crosslinking network in a curable polymercomposition such that the polymer forms a structure that issubstantially insoluble in solvents for the uncrosslinked polymer.

The term “bisphenol-A” refers to 2,2-bis(4-hydroxyphenylpropane).

Unless otherwise specified herein, the term “viscosity” refers to theviscosity of a polymer in styrene monomer at 65 wt. % NVM (non-volatilematerial, see below) at 25 C measured using a Brookfield Viscometer.

The term “NVM” refers to non-volatile material (a.k.a. “solids”)dispersed in a volatile substance (e.g., styrene monomer) measuredaccording to ASTM D1259.

The term “ASTM” refers to a well known collection of standard laboratoryprocedures for measuring the properties of materials published by theAmerican Society for Testing and Materials.

Unless specified otherwise, all ratios, percentages, and parts are byweight.

A more detailed description of the aromatic polyol end-cappedunsaturated poly-etherester resins and the curable thermoset resincompositions, and the corresponding methods of making and using them, ofthis invention follows.

Aromatic Polyol End-Capped Unsaturated Polyetherester Resin

The aromatic polyol end-capped unsaturated polyetherester resins of thisinvention are obtainable by a process comprising reacting at least oneacid-terminated unsaturated polyetherester resin with at least onearomatic polyol having at least one non-primary hydroxy group,preferably at least one secondary hydroxy group, to produce anunsaturated polyetherester resin at least partially end-capped with anaromatic polyol.

Suitable acid-terminated unsaturated polyetherester resins for makingthe corresponding end-capped resins include the reaction products ofpolyethers and unsaturated carboxylic anhydrides or unsaturated di-orpolycarboxylic acids. Preferred polyethers include polyether polyols,such as polyoxyalkylene polyols, alkylene oxide-alkylene oxidecopolymers, and the like, in which the alkylene group preferably hasfrom 2 to 6 carbon atoms (for example, polyoxypropylene polyols,polyoxyethylene polyols, ethylene oxide-propylene oxide copolymers,etc.). These polyols preferably have average hydroxyl functionality inthe range from about 2 to about 8 and preferably have a number averagemolecular weight in the range from about 250 to about 10,000. Theunsaturated anhydrides are preferably cyclic anhydrides, such as maleicanhydride, succinic anhydride, phthalic anhydride, and the like.Preferred unsaturated di-or polycarboxylic acids include linear,branched, and cyclic C₃-C₄₀ dicarboxylic acids and C₈-C₄₀ aromaticdicarboxylic acids, such as maleic acid, fumaric acid, phthalic acid andisophthalic acid.

This reaction is conducted under reaction conditions that assure that atleast some of the unsaturated polyetherester is acid-terminated, whichcan be determined by one of ordinary skill in this field. One skilled inthe art would know how to adjust the reaction conditions, such as theratio of the number of equivalents of the acid reactant(s) to the numberof equivalents of the polyol reactant(s) to obtain an unsaturatedpolyetherester resin product with acid-terminated polymer chains. Theratio of equivalents of acid reactant(s) to polyol reactant(s) ispreferably at least about 0.7:1., more preferably at least about 0.9:1,and even more preferably at least about 1:1.

The oxyalkylene repeat units of the preferred unsaturated polyetheresterresins have from 2 to 10 carbon atoms each (e.g., oxypropylene,oxyethylene, etc.), more preferably from 2 to 4 carbon atoms.Preferably, the unsaturated polyetherester resins have an ether/estermole ratio of at least about 0.75, more preferably at least about 1 andpreferably not greater than about 3. The number average molecular weightof these resins is preferably in the range from about 500 to about10,000.

U.S. Pat. No. 5,319,006, which is incorporated herein by reference,describes one process for making the unsaturated polyetherester resinsin which the polyether is reacted with a cyclic unsaturated carboxylicanhydride in the presence of a Lewis acid catalyst.

U.S. Pat. Nos. 5,436,313 and 5,436,314, also incorporated herein byreference, describe preferred methods for preparing the unsaturatedpolyetherester resins in which the catalyst for inserting anhydrides anddicarboxylic acids into the polyethers are protic acids having a pKaless than about 0 and metal salts thereof.

The above-described acid-terminated unsaturated polyetherester resin is,according to the process of making the aromatic polyol end-cappedproduct of this invention, reacted with at least one aromatic polyol.The reaction lowers the acid number of the acid-terminated unsaturatedpolyetherester resin relative to the acid number of the same prior tothe reaction. Preferably, the acid number of the unsaturatedpolyetherester resin is decreased by at least 50 percent via thereaction with the aromatic polyol. In a preferred embodiment, the amountof the at least one aromatic polyol reacted with the acid-terminatedunsaturated polyetherester resin is at least about 5, more preferably atleast about 10, up to about 50, wt. % based on the total weight of thestarting reaction mixture.

Aromatic polyols suitable for reacting with the acid-terminatedunsaturated polyetherester resin to make the aromatic polyol end-cappedproduct of this invention has at least one nonprimary hydroxy group asone of the polyol hydroxy groups. The aromatic polyol can have multiplenonprimary hydroxy groups. The nonprimary hydroxy groups may besecondary and tertiary hydroxy groups, but are preferably secondaryhydroxy groups. Preferably, the aromatic polyol also has at least oneprimary hydroxy group as one of the polyol hydroxy groups to increasethe overall reaction rate between the aromatic polyol and theacid-terminated unsaturated polyetherester. A wide range of aromaticpolyols are suitable as the reactant(s) with the unsaturatedpolyetherester resin.

In a preferred embodiment, the aromatic polyol may be represented by thefollowing formula:

wherein Ar₁, Ar₂ and Ar₃ each independently represents an aromaticgroup; R₁, R₂ and R₃ each independently represents a non-aromaticpredominantly hydrocarbyl group; each X and X′ independently representsa hydrocarbylene group, a hydrocarbylidene group, a divalent hetero atomor group, an ester linkage, or a combination thereof; each X′ can alsorepresent a covalent bond; h and k each independently represent aninteger equal to 0 or 1; j represents an integer in the range from 0 to5; and m, n, and p each independently represent an integer in the rangefrom 1 to 5, provided that at least one hydroxy group of formula (I) isa nonprimary hydroxy group. Formula (I) dictates that subscripts j and kare equal to 0 when h is 0.

Ar₁, Ar₂ and Ar₃ are preferably substituted or unsubstituted phenylgroups, more preferably unsubstituted phenyl groups, wherein thesubstituted phenyl groups are preferably substituted with one or morehydrocarbyl groups, hetero groups and hetero atoms, preferablyhydrocarbyl groups. R₁, R₂ and R₃ are preferably aliphatic groups havingup to about 12, more preferably up to about 8, and even more preferablyup to about 4, carbon atoms. X is preferably a hydrocarbylene orhydrocarbylidene group, even more preferably a nonaromatichydrocarbylene or hydrocarbylidene group, such as a straight or branchedalkylene or alkylidene group, respectively, and even more preferablymethylene or an alkylidene group having from 2 to 8 carbon atoms, morepreferably from 2 to 4 carbon atoms, such as propylidene. X′ ispreferably a divalent hetero atom, such as an oxygen atom, or a divalentether or ester group. When h is 1 and k is 0, X is preferably analkylidene, more preferably a propylidene, group in which the group isbonded to the rest of the molecule solely at a nonprimary carbon atom.When j is in the range from 1 to 5 and in at least some, preferably all,j units k is 1, X is preferably a methylene group.

In one preferred embodiment, k equals 0. Those aromatic polyols may alsobe referred to as monoaromatic diols. Preferred monoaromatic diols arerepresented by the following formula:

wherein R₄ to R₇ each independently represent a hydrogen atom or ahydrocarbyl group, provided that at least one hydroxy group is anonprimary hydroxy group. The hydrocarbyl group is preferably analiphatic group having from 1 to 6 carbon atoms, more preferably analkyl group having from 1 to 3 carbon atoms, and even more preferably amethyl group; X′ is as defined above, preferably an ether or esterlinkage or a covalent bond; and m and n are integers as defined above,preferably equal to 1. Specific examples of monoaromatic diols includebis-(β-hydroxypropyl)isophthalate, bis-(β-hydroxypropyl)terephthalate,bis-(β-hydroxypropyl)phthalate, tetramethyl 1,4-benzenedimethanol, andtetramethyl 1,3-benzenedimethanol. Monoaromatic diols in which at leastone hydroxy group is a nonprimary, more preferably a secondary, hydroxygroup are preferred. In some embodiments, those monoaromatic diols inwhich one hydroxy group is a primary hydroxy group and the other hydroxygroup is a nonprimary hydroxy group are even more preferred.

In another preferred embodiment of this invention, the aromatic polyolend-capped polyetherester resin is obtainable by reacting theabove-described unsaturated polyetherester resin with an aromatic polyolrepresented by the formula:

wherein each of R₈ to R₁₃ represent a hydrogen atom or a predominantlyhydrocarbyl group, provided that at least one of R₈ and R₉ is not anhydrogen atom, and more preferably in some cases one is hydrogen and theother is a predominantly hydrocarbyl group; X represents —C(CH₃)₂—, —S—or —O—, preferably —C(CH₃)₂—; and m and n represents integers whichindividually are in the range from 1 to 5. The predominantly hydrocarbylgroup is preferably a methyl group.

Preferred compounds of formula (III) in which m and n are each equal to1 may be obtained by reacting the appropriate diol compound with theappropriate bisphenol compound under conditions ascertainable by one ofthe ordinary skill in the field of organic chemistry without undueexperimentation. A preferred example of such a reaction is that betweenpropylene glycol and bisphenol A. The product of the latter preferredreaction is commercially available as Dow Resin 565 (The Dow ChemicalCompany) and also as SYNFAC® 8029 (Millikan & Company).

Preferred compounds of formula (III) in which m and n may be greaterthan 1 may be obtained by making an adduct of an appropriate bisphenolcompound using an appropriate alkylene oxide under conditionsascertainable by one of ordinary skill in the field of polymer chemistrywithout undue experimentation. A preferred compounds of this typeinclude propylene oxide adducts of bisphenol A, such as UCAR™ Diol 3P,available from Union Carbide Corp. Other examples include UnionCarbide's UCAR™ Diol BB-300 and Millikan & Company's SYNFAC® Polyols.

In another preferred embodiment of this invention, the aromatic polyolused to make the end-capped polyetherester resin is at least onecompound of formula (I) in which h and k are each equal to 1, and j isin the range from 2 to 5. Such aromatic polyols and how to make them areknown in the field of organic chemistry. Examples of such compoundsinclude novolac-type polyols obtainable by alkoxylating a novolac-typeresin. A novolac-type resin is defined herein as either (1) a novolacresin produced by reacting phenol or substituted phenols with analdehyde, such as formaldehyde or (2) resins produced by coupling phenolor substituted phenols with a divinyl linking compound and optionallymodifying with mono-styrenics. The first type are old and readilyavailable on the market, and can easily be synthesized by one ofordinary skill in the polymer chemistry field. The second are describedin U.S. Pat. No. 5,674,970, which is incorporated herein by reference,and which are commercially available from Georgia-Pacific Resin Co.under the trademark ARYLZENE™. An example is ARYLZENE™ 7040.

Polyols of ARYLZENE™ that are suitable for use as the aromatic polyolreactant for making the aromatic polyol end-capped polyetherester resinsof this invention are also commercially available from Georgia-PacificResin. An example of such an ARYLZENE™ polyol is ARYLZENE™ 7140 polyol,the result of propoxylation of an ARYLZENE™ resin.

In a preferred embodiment, these aromatic polyols may be represented bythe formula:

wherein X, X′, h, j, k, m, n and p are as previously defined in formula(I) above. In a more preferred embodiment, X represents methylenegroups. In an even more preferred embodiment, k is 1 and j is in therange from 1 to 3.

End-capping compounds that may be present in addition to aromaticpolyols include, for example, dicyclopentadiene, an epoxy-containingcompound, or both dicyclopentadiene and an epoxy-containing compound.The epoxy-containing compound may be selected from those described belowin connection with the additional unsaturated polyetherester resin underthe subheading “Optional Ingredients”.

The aromatic polyol end-capped unsaturated polyetherester resinsobtainable according to the above process increase the water and/orchemical resistance of curable thermoset resin compositions to whichthey are added without decreasing the storage stability of thosecompositions prior to adding curing agent. Another advantage of theend-capped polyetherester resins according to this invention is thatthey have the advantage of improving the ease of application of thecurable thermoset resin compositions in which they are incorporated andreduce styrene emissions.

The low viscosity of the end-capped resins contributes to the latteradvantages. In a preferred embodiment, the end-capped polyetheresterresins according to this invention have a viscosity not greater thanabout 1200 cp (1.200 Pa·s) when the resin is dissolved in 35 wt %styrene based on the total weight of resin and styrene.

Unsaturated Polyester Resins

The unsaturated polyester resins suitable as component (B) of thecurable thermoset resin compositions, and intermediate therefore, ofthis invention are those that are commonly employed to makefiber-reinforced composite materials. They are well known, in that theyare described in numerous issued patents, and they are readily availablecommercially.

Preferably, the unsaturated polyester resin component (B) is adicyclopentadiene (DCPD) polyester resin obtainable from DCPD, maleicanhydride and a polyhydric alcohol. The polyhydric alcohol is preferablya glycol (e.g., propylene polyhydric alcohol, ethylene polyhydricalcohol, diethylene polyhydric alcohol, dipropylene polyhydric alcohol,or mixtures of these). The reaction is preferably performed in thepresence of water under conditions to generate maleic acid from themaleic anhydride so as to form DCPD maleate and then esterifying themaleate with the glycol to form the unsaturated polyester resin. TheDCPD polyester resin preferably has a viscosity not greater than about500 cp (0.50 Pa·s).

The preparation of DCPD polymer resins is described, for example, inU.S. Pat. Nos. 3,933,757; 3,347,806; 3,883,612; 4,029,848; 4,148,765;4,348,499; and 4,246,367, the teachings of which are incorporated hereinby reference.

DCPD polyester resins are typically available as solutions in vinylaromatic monomers such as styrene. To the extent that the vinyl aromaticmonomer is already introduced by the DCPD polyester resin solution, thatcounts towards the presence of vinyl monomer component (C).

The proportion of DCPD polyester resin to polyetherester resin fallswithin a weight ratio range of about 10:90 to about 90:10, andpreferably within the range from about 25:75 to about 75:25.

Vinyl Aromatic Monomers

The vinyl aromatic monomers useful as component (C) of the curablethermoset resin compositions, and intermediate therefore, of thisinvention include styrene, vinyl toluene, chlorostyrenes,tert-butylstyrene, dimethylstyrenes, divinylbenzene, diallylphthalate,mono- or multifunctional lower alkyl esters of acrylic and methacrylicacids, and the like, and mixtures thereof. Styrene is preferred. Thevinyl aromatic monomer is present in an amount effective to result in acured thermoset when reacted with the other components of the curablethermoset resin composition in the presence of a free-radical initiator.The amount of vinyl aromatic monomer in the curable thermoset resincomposition is in the range from about 10 to about 70 wt. %. Preferably,the vinyl monomer is present in an amount of at least about 20 wt. %,more preferably at least about 30 wt. %, up to about 60 wt. %, morepreferably up to about 50 wt. %, and even more preferably up to about 36wt. %.

Curing Agent

The curing agent useful as component (D) of the curable thermoset resincompositions of this invention comprises at least one free-radicalinitiator. Useful free-radical initiators are those well known andcommercially available in the unsaturated polyester industry. Theyinclude peroxide and azo-type initiators. Peroxide initiators include,for example, methylethyl ketone (MEK) peroxide, benzoyl peroxide,tert-butylperbenzoate, ter-butylperoxide, and the like, and mixturesthereof. An example of a commercially available initiator is THERMACURE®JTS (a methyl ethyl ketone peroxide available from Cook Composites andPolymers, Inc.). The initiator is used in an amount effective to reactthe vinyl aromatic monomer and other polymer components of the curablethermoset resin composition to produce a cured thermoset. Typically, theamount is within the range from about 0.5 to about 3 wt. %, morepreferably from about 1 to about 2 wt. %, based on the weight of thecurable thermoset resin composition.

An accelerator is often combined with the free-radical initiator in thecuring agent to allow curing at lower temperatures. Examples ofaccelerators include dimethylaniline and salts of transition metals(cobalt, iron, manganese, copper, zinc, or vanadium), such as cobaltnaphthenate, cobalt octanoate, and the like.

Optional Ingredients

The curable thermoset resin compositions, and intermediates for makingthem, according to the present invention may contain additional optionalingredients. One of those optional ingredients is at least one aromaticvinyl ester resin. This ingredient may be added to provide furtherimprovements in properties, such as even higher resistance to solventsand chemicals, including resistance to acidic oxidizing environments,and improved strength and toughness at elevated temperatures. Examplesof aromatic vinyl ester resins include products obtainable by reacting avinyl acid, such as acrylic or methacrylic acid, with an epoxyend-capped phenolic compound. The epoxy end-capped phenolic compound istypically an epoxy adduct of bisphenol A or a novolac resin, which areobtainable by reacting the bisphenol A or novolac resin, respectively,with epichlorohydrin. Vinyl ester resins and how to make them aredescribed in U.S. Pat. No. 4,525,544, which is incorporated herein byreference.

Such aromatic vinyl esters are commercially available from The DowChemical Company under the trademark DERAKANE™. An example of anaromatic vinyl ester resin which is derived from an epoxy end-cappedbisphenol A is DERAKANE™ 411. Aromatic vinyl ester resins derived fromepoxy end-capped novolac resins are designated DERAKANE™ 470.

The curable thermoset compositions and intermediates for making them, inthis invention, may also further comprise as additional optionalingredients at least one unsaturated polyetherester resin other than theunsaturated polyetherester resin (A) of the invention already defined.This additional unsaturated polyetherester resin may be end-capped withat least one end-capping compound selected from the group consisting ofdicyclopentadiene, an epoxy-containing compound, or bothdicyclopentadiene and an epoxy-containing compound.

The epoxy group-containing compound may be represented by the followingformula:

wherein R¹, R² and R³ represent a hydrogen atom or a hydrocarbyl groupoptionally having one or more hetero atoms, provided that at least oneof R¹, R², and R³ is not a hydrogen atom. The hydrocarbyl group may bemethyl, aliphatic, cycloaliphatic, or aromatic, combinations of two ormore of methyl, aliphatic, cycloaliphatic and aromatic moieties, with orwithout hetero atoms. The hetero atoms may, for example, be oxygen orsulfur atoms present as ether or ester linkages between two or moremethyl, aliphatic, cycloaliphatic, or aromatic moieties and/or thehetero atoms may be present in functional groups, such as additionalgroups of formula (V). The hydrocarbyl group preferably does not containfunctional groups reactive with the epoxy group on formula (V).Preferably, the epoxy-containing compound has at least two hydrocarbylgroups that do not contain moities reactive with the polyetheresterresin (A).

The number average molecular weight of the epoxy-containing compound ispreferably no greater than 1500, preferably no greater than about 1000,and even more preferably no greater than 500. The epoxy group-containingcompounds include, for example, glycidyl esters, glycidyl ethers, epoxyalkyls, epoxy cycloalkyls, epoxyalkylenes, aromatic epoxy compounds,such as p-glycidyl-styrenes, and the like, and mixtures thereof.Specific examples of the epoxy group-containing compounds includeCARDURA® Resins (glycidyl esters available from the Shell Oil Company)such as CARDURA® E-10 Resin (a glycidyl ester of Versatic™ 10 Acid;GLYDEXX® available from Exxon Chemical Co., such as GLYDEXX® N-10 orND-101; etc.

Suitable aromatic epoxy compounds include glycidyl ethers obtainable bythe reaction of epichlorohydrin with an aromatic compound containing atleast one hydroxyl group carried out under alkaline reaction conditions.The epoxy-containing compounds obtained when the hydroxylgroup-containing compound is 2,2-bis(4-hydroxy-phenylpropane)(i.e.,bisphenol-A) are represented by the structure below wherein n is zero ora number greater than 0, commonly in the range of 0 to 10, preferably inthe range of 0 to 2.

Other suitable epoxy compounds can be prepared by the reaction ofepichlorohydrin with mononuclear di- and tri-hydroxy phenolic compoundssuch as resorcinol and phloroglucinol, selected polynuclear polyhydroxyphenolic compounds such as bis(p-hydroxyphenyl) methane and4,4′-dihydroxybiphenyl, or aliphatic polyols such as 1,4-butanediol andglycerol.

Preferred diepoxy compounds include those designated EPON® Resincommercially available from the Shell Oil Company, such as EPON® Resins825, 826 and 828, each of which are reaction products of epichlorohydrinand bisphenol A in which the n value of the above formula is 0.04, 0.08and 0.13, respectively. The commercially-available epoxy resin EPON®Resin 828 having a molecular weight of about 400 and an epoxideequivalent (ASTM D-1652) of about 185-192, is a preferred diepoxycompound because of its low viscosity, mechanical performance andcommercial availability.

Additional examples of suitable bisphenol-A type epoxy compounds includethe D.E.R.™ resins available from The Dow Chemical Company, such asD.E.R.™ 330, 331, 332 and 383 and the ARALDITE™ GY resins available fromCiby-Geigy such as ARALDITE™ GY 6004, 6005, 6008, 6010 and 2600.

In a preferred embodiment, the at least one end-capping compoundcomprises at least some, more preferably at least about 20 wt. %, evenmore preferably at least about 50 wt. % and preferably less than orequal to about 80 wt. %, DCPD and/or monofunctional epoxy-containingcompound, which may be obtainable by reacting the same with theunsaturated polyetherester resin in the corresponding proportions. Inone embodiment, the at least one end-capping compound comprises amixture of (a) DCPD and/or monofunctional epoxy-containing compound and(b) a di-or polyfunctional epoxy-containing compound, preferably whereinthe ratio of (a) to (b) is in the range from about 10:90 to about 90:10,more preferably from about 20:80 to about 80:20.

Further components may be added to the curable thermoset resincompositions of this invention. Such components include reinforcingagents such as fibers, for example glass, fibers or organic fibers,which may be in chopped form or in the form of a fabric or mat; fireretardants (phosphorous or antimony compounds, aluminum trihydrate,halogenated waxes, etc.), antioxidants, free radical initiatorinhibitors (e.g., to prevent premature initiation of polymerization),pigments, colorants, mold release agents, inert fillers (calciumcarbonate, clays, talc, etc.), low-profile or low-shrink additives,thickeners (magnesium oxide, magnesium hydorxide, calcium oxide, etc.),etc. When reinforcing fiber is used, the amount of fiber is preferablyat least 5 wt. %, more preferably at least about 10 wt. %, up to about80 wt. %, more preferably up to about 60 wt. %, of the total weight ofthe composition.

Utility of the Curable Thermoset Resin Composition

The curable thermoset resin compositions of this invention, whencombined with a reinforcing fiber may be used to obtain afiber-reinforced polymer composite by curing the thermoset resincomposition.

The curable thermoset resin composition of this invention may also beused to prepare an intermediate for making a skin laminate by combiningthe curable thermoset resin composition with reinforcing fibers in theform of a sheet preferably having an average cross-sectional thicknessof at least about 10 mil (0.25 mm), more preferably from about 20 mil(0.5 mm) up to about 200 mil (5 mm), more preferably up to 100 mil (22.5mm), even more preferably up to 30 mil (0.8 mm). The fiber content ofthe skin laminate is preferably in the range from about 25 to about 45wt. %. The fiber is preferably about 0.5 inch to about 2 inch (about 1to about 5 cm) chopped fiber or a shear of a continuous strand fibermat. The skin laminate intermediate may be used between a gel coat layerand a fiber-reinforced polymer layer in a gel coated polymer laminate toimprove water and/or chemical resistance and also to improve the surfaceappearance of the laminate.

Water and/or chemical resistance of the gel coated polymer laminate mayalso be improved by interposing just the curable thermoset resincomposition, with or without optional components, between the gel coatlayer and the fiber-reinforced polymer layer.

An advantage of interposing the thermoset resin of the present inventionbetween a gel coat layer and the fiber-reinforced polymer layer is theprevention, or minimization, of blistering due to the migration of waterand/or other low molecular weight substances, such as organic solvents,through the gel coat into the fiber-reinforced polymer, causingswelling, delamination, and other problems in the fiber-reinforcedpolymer layer. The swelling can cause a blister under the gel coat andcontinued migration of water and/or other solvents into thefiber-reinforced polymer can eventually lead to loss of strength in thefiber-reinforced polymer laminate.

In one embodiment, blistering of a gel coated fiber-reinforced polymeris reduced by applying at least one layer of the curable thermoset resincomposition or the skin laminate intermediate between the gel coat layerand the fiber-reinforced polymer layer and curing the curable thermosetresin composition. Preferably, this is carried out by applying a gelcoat composition to a mold, at least partially curing the gel coatcomposition, applying at least one curable thermoset resin compositionor the skin laminate intermediate to the at least partially cured gelcoat, at least partially curing the curable thermoset resin composition,applying at least one fiber-reinforced polymer layer to the at leastpartially cured thermoset resin composition layer, and curing theresulting product to form the gel coated fiber-reinforced polymer.

The polyester resin used to make the fiber-reinforced polyester resinmay be any general purpose polyester resin known in the art, such asorthophthalic acid-based polyester resins. Preferred polyester resinsare those with a molecular weight/double bond or vinyl group (—C═C—)factor between about 150 and about 500, more preferably between about200 and about 350 (as further described in U.S. Pat. Nos. 3,701,748;4,295,907; and 5,637,630 which are incorporated herein by reference).These resins are made from a reaction of one of more glycols with anunsaturated dicarboxylic acid or its anhydride or with a mixture of theunsaturated acid or its anhydride with a saturated dicarboxylic acid orits anhydride. The reaction mixture may also include dicyclopentadieneto control the molecular weight of the polyesters as described in U.S.Pat. Nos. 3,883,612 and 3,986,922, which are incorporated herein byreference. The unsaturated polyester resin typically has a numberaverage molecular weight in the range from about 500 to about 5,000,preferably in the range from about 700 to about 2,000. Examples ofsuitable unsaturated polyester resins include the STYPOL® polyesterresins made by Cook Composites & Polymers, Inc. The polyester resin isapplied as a matrix precursor and then cured, for example, by using acuring agent described above for the polyetherester resin.

The gel coat composition may be any of those that are well known andavailable in the art. The gel coat is typically 10 to 25 mils (0.2 to0.6 mm) in thickness, and is the surface coating of the molded part. Thegel coat provides the finishing color and surface profile of the part.Gel coats are well known and various grades are commercially available.The selection of gel coat will depend upon the desired characteristicsof the part relative to, among other things, weatherability, hydrolyticstability, and surface finishing. Examples of commercially available gelcoat materials include gel coat materials available from Cook Compositesand Polymers under the marks POLYCOR®, ARMORCOTE®, BUFFBACK®,ENVIROCOR®, and LOVOCOR®.

Examples of the various types of reinforcement fibers that can be usedin the practice of this invention are glass fibers, carbon fibers,various aramid fibers, and other types of natural and synthetic fibers.The typical fiber content of the composite is between about 10 and 80percent by weight.

The composite and the molded part can, and often are, constructed in oneoperation. First, a gel coat is usually applied to the surface of themold, at least partially cured, and then a skin laminate is applied overthe at least partially cured gel coat. These are open mold operations.Then the fiber-reinforced polyester matrix precursor is applied, forexample, by hand lay-up or spray-up, or the fiber reinforcement isapplied to the skin laminate, the mold is closed, and the polyestermatrix precursor is injected into the closed mold, preferably with theclosed mold under vacuum. The precursor is then allowed to cure, with orwithout a heat supplement, and the part or article demolded.

EXAMPLES

Resin A

Resin A is an end-capped unsaturated polyetherester resin according tothis invention blended with styrene monomer. The unsaturatedpolyetherester resin is prepared by charging a 5 liter flask, equippedwith an agitator, condenser, thermometer and sparge tube for introducingnitrogen gas, with 1,050 grams ACCLAIM™ Polyol 2200 (a 2000 MWpolyoxpropylene diol available from ARCO Chemical Co.), 395 gramspropylene glycol, 1020 grams maleic anhydride and 2.3 gramsp-toluenesulfonic acid monohydrate and heating the mixture to 195 C for4 hours while introducing nitrogen gas until the acid number drops to110 mg KOH/g. End-capping is conducted by reducing the temperature ofthe reaction mixture to 150 C, introducing 760 gbis-(β-hydroxypropyl)isophthalate to the resulting mixture, and raisingthe temperature back to 195 C, where it is maintained until the acidnumber is reduced to 30 mg KOH/g. The reaction product is blended with1750 g styrene monomer to form about 5,000 g of a clear resin solutioncontaining the end-capped resin (Resin A) having a viscosity of 400 cp(0.400 Pa.s) and 65 wt. % NVM.

Resin B

Resin B is also an end-capped unsaturated polyetherester resin accordingto this invention blended with styrene monomer. The end-cappedunsaturated polyetherester resin is prepared the same way as that ofResin A, except that 760 g Dow Resin 565(2,2-bis(4-(β-hydroxypropoxy)phenylpropane) commercially available fromThe Dow Chemical Co.) is added instead of 760 gbis-(β-hydroxypropyl)isophthalate as the end-capping reagent. Theresulting end-capped unsaturated polyetherester resin (Resin B) blendedwith styrene monomer has a viscosity of 500 cp (0.500 Pa.s) and 65 wt. %NVM.

Resin C

Resin C is another end-capped unsaturated polyetherester resin accordingto this invention blended with styrene monomer. The end-cappedunsaturated polyetherester resin is prepared the same way as that ofresin A, except that 760 g of ARYLZENE 7140 (a propoxylated product ofaralkylation of compounds containing phenolic hydroxyls commerciallyavailable from Georgia-Pacific Resin Company). The resulting end-cappedunsaturated polyetherester resin (Resin C) blended with styrene monomerhas a viscosity of 500 cp (0.500 Pa.s) and 65 wt. % NVM.

Resin D (Comparative)

Resin D is an epoxy end-capped unsaturated polyetherester resin blendedwith styrene monomer used for the comparative examples which follow.This unsaturated polyetherester resin is prepared by charging a 5 literflask, equipped with an agitator, condenser, thermometer and sparge tubefor introducing nitrogen gas, with 1418 grams ACCLAIM™ Polyol 2200 (a2000 MW polyoxpropylene diol available from ARCO Chemical Co.), 442grams propylene glycol, 1140 grams maleic anhydride and 2.3 gramsp-toluenesulfonic acid monohydrate and heating the mixture to 195 C for4 hours while introducing nitrogen gas until the acid number drops to110 mg KOH/g. End-capping is conducted by reducing the temperature ofthe reaction mixture to 140 C, introducing 260 g DCPD dropwise to theresulting mixture, and maintaining the 140 C temperature for 4 hoursuntil the acid number is reduced to about 84 mg KOH/g. The mixture isthen charged with 0.7 g DMP-30 (2,4,6-trisdimethylaminomethylphenol),mixed and maintained at 140 C for 5 minutes, after which 675 g EPON®Resin 828 (available from the Shell Oil Co.) is added, the reactionmixture continues to be mixed and is maintained at a temperature of140-150 C until the acid number drops to 30 mg KOH/g. The reactionproduct is blended with 1500 g styrene monomer to form about 5,000 g ofa clear resin solution containing the end-capped resin (Resin D) havinga viscosity of 1100 cp (1.100 Pa.s) and 65 wt. % NVM.

Resin E (Comparative)

Resin E is a propylene glycol end-capped unsaturated polyetheresterresin blended with styrene monomer for use in a comparative exampledescribed below. The unsaturated polyetherester resin is prepared bycharging a two liter resin kettle, equipped with a mechanical stirrer,nitrogen sparge tube, thermocouple, and distillation head, with 975 gARCOL™ LG56 (a polyoxypropylene triol having a molecular weight of about3000 available from ARCO Chemical Co.), 525 g maleic anhydride, and 1.5g p-toluenesulfonic acid, and heating the mixture to 55 C until ahomogeneous solution results. 152 g water is then added and the mixtureis stirred until the exotherm from the hydrolysis reaction of maleicanhydride and water dissipates. The temperature of the mixture is thengradually increased to 185 C and the mixture is held at that temperatureuntil the acid number drops to 138 mg KOH/g. 243 g propylene glycol isadded and heating is continued until the acid number is reduced to 53 mgKOH/g. After vacuum stripping, a clear, nearly water-white, resinresults (Resin E). This resin is blended with styrene to form a mixturehaving 65 wt. % NVM.

DCPD Resin

DCPD resin is a DCPD unsaturated polyester resin blended with styrene.The DCPD unsaturated polyester resin is prepared by charging a 4 literresin kettle, equipped with a mechanical stirrer, nitrogen sparge tube,thermocouple (for measuring temperature), and a distillation head, with1032 g maleic anhydride, heating the maleic anhydride to 150 F (66 C),slowly adding about 207 g water to the maleic anhydride and allow thetemperature to rise to about 245 F (118 C) due to the heat given off bythe exothermic reaction between the maleic anhydride and the addedwater, and then, when the temperature begins to drop of its own accord,adding 1392 g DCPD at a rate that maintains the temperature of thereactants between about 245 and 265 F (between about 118 C and 129 C)until the acid number of the reaction mixture is 245 KOH/g or less. Then415 g of ethylene glycol are added to the resulting reaction mixture andthe temperature of the reaction mixture is raised to 400 F (204 C) andmaintained at about that temperature until the acid number drops to 42KOH/g. A vacuum (i.e., negative pressure differential) of 25 inches Hg(85 kPa) is applied to the mixture for about 30 minutes as the reactiontemperature is allowed to cool. The reaction product is then blendedwith 1200 g styrene.

Preparation of the Curable Thermoset Resins

Resins A, B, D, and E are each combined with the above described DCPDResin in the proportions shown in Table 1 below to make Examples 1-3 ofthis invention and comparative Examples C-1 and C-2. A catalyst systemis added to cure each example at room temperature, which consists of1.25 wt. % THERMACURE® JTS (a methyl ethyl ketone peroxide availablefrom Cook Composites and Polymers, Inc.), 0.15 wt. % cobalt naphthenate,and 0.12 wt. % N,N-dimethylacetoacetamide. The results obtained areshown in Table 1 below.

TABLE 1 Result of Curing Examples 1-3 of the Invention and ComparativeExamples C-1 and C-2 Component/Property Ex. 1 Ex. 2 C-1 C-2 Ex. 3 DCPDResin (g) 70 70 70 70 50 Resin A (g) 30 — — — 35 Resin B (g) — 30 — — —Resin D (g) — — 30 — — Resin E (g) — — — 30 — Derakane — — — — 15 470-36VE (g) NVM (wt. %) 65 65 65 65 65 Viscosity (cp) 241 281 340 200 310 GelTime (min.) 25.0 20.4 21.9 21.5 23.6 Gel to Peak 11.1 9.8 10.7 9.8 10.9Exotherm (min.) Maximum Exotherm (F) 344 349 355 359 350 HDT (F) 204 216204 211 231

Gel time and viscosity of these compositions when they are stored forvarious periods of time prior to adding the crosslinking agent is shownbelow in Table 2.

TABLE 2 Stability of Gel Time and Viscosity During Storage Resin B ResinD Resin E Gel Time (min.)  0 day 21.0 21.5 20.5 15 days 23.0 31.0 22.530 days 26.0 34.0 23.0 Viscosity (cp)  0 day 450 1020 400 15 days 5101150 420 30 days 500 1320 410

As can be seen from Table 2, the storage stability of Resin B accordingto this invention is substantially greater than the storage stability ofcomparative epoxy end-capped Resin D and roughly the same as the storagestability of comparative Resin E.

Gel coated laminates are prepared by spraying a full ISO/NPG type of gelcoat on a glass mold, drawing down the gel coat to 23 and 48 mil (0.58and 1.22 mm) “wet” thickness, and then letting the gel coat cure for 1hour at ambient temperature. A skin laminate is applied to the gel coatconsisting of 2 plies of 1.5 ounce (42.5g) fiberglass mat saturated withone of Examples 1-3 and Comparative Examples C-1 and C-2 of Table 1,such that each skin laminate had a 30 wt. % glass content. The cure timefor skin laminate is 2 hours at ambient temperature. The main laminateconsisting of 4 plies of 1.5 ounce (42.5g) fiberglass mats with 30 wt. %glass content is applied after the skin laminate. A typical marine gradelaminate resin, STYPOL® 40-4822, is used. The laminate is cured atambient temperature for at least 16 hours before the water boil test wasperformed. Table 3 shows the surface profile ratings. (Based on ACT™Orange Peel Standards).

TABLE 3 Surface Rating of Gel Coated Laminates Ex. 1 Ex. 2 C-1 C-2 Ex. 3Initial (thin): Longwave, mean 10.7 8.7 8.5 8.8 8.1 Shortwave, mean 7.85.4 9.2 8.9 5.4 Rating, mean 6.7 7.2 7.3 7.1 7.4 Initial (thick):Longwave, mean 2.1 2.8 2.1 1.9 1.4 Shortwave, mean 5.7 5.7 4.7 3.1 3.6Rating, mean 10.2 9.6 10.3 10.4 10.5

The waviness rating values (ACT™ Orange Peel Standards) are typicalindustry visual test methods used to describe the surface appearance ofan object. A BYK-Gardner wave-scan is used to measure the surfaceappearance of various test panels. The wave-scan can report the resultsin both long-term (structure size greater than 0.6 mm) and short-termwaviness (structure size less than 0.6 mm). Both long-term andshort-term waviness are rated from 0 to 100. The higher the number, themore waviness is observed. The long-term and short-term waviness arethen mathematically correlated to a surface rating value from 0 to 10.The higher the number, the smoother the surface appears. As can be seenfrom Table 3, the surface ratings are similar between the examplesaccording to this invention and the comparative examples.

The gel coated laminates described above are then exposed to boilingwater for 100 hours and then the surface profiles are rated according toa procedure which generates an “ANSI Rating”. The “ANSI Rating” refersto a surface profile test described in the publication ANSIZ124.1-1987section 6.3 issued by ANSI (the American National Standards Institute).A lower ANSI rating indicates better surface profile. An ANSI ratinggreater than 9 is considered failure.

TABLE 4 ANSI Ratings for Panels Exposed to Boiling Water for 100 HoursEx. 1 Ex. 2 C-1 C-2 Ex. 3 ANSI Rating (thin) 6.1 6.2 6.7 8.0 5.9 ANSIRating (thick) 3.1 3.8 4.0 4.7 3.9

As shown by Table 4, the panels according to this invention have waterresistance at least as good as the comparative examples when the gelcoat is thick, and show improved water resistance when the gel coat isthin, which is when the laminate is most prone to surface profiledeterioration.

The preceding examples are for illustrative purposes only. They are notto be construed as a limitation upon the invention as described in thefollowing claims.

What is claimed is:
 1. A curable thermoset resin composition,comprising: (A) at least 5 wt. % of at least one unsaturatedpolyetherester resin at least partially end-capped with an aromaticpolyol comprising at least one non-primary hydroxy group, the aromaticpolyol represented by the formula

wherein Ar₁, Ar₂ and Ar₃ each independently represents an aromaticgroup; R₁, R₂ and R₃ each independently represents a non-aromaticpredominantly hydrocarbyl group; each X and X′ independently representsa hydrocarbylene group, a hydrocarbylidene group, a divalent heteroatomor group, an ester linkage, or a combination thereof; each X′ can alsorepresent a covalent bond; h and k each independently represent aninteger equal to 0 or 1; j represents an integer in the range from 0 to5; and m, n, and p each independently represent an integer in the rangefrom 1 to 5, provided that at least one hydroxy group of formula (I) isa nonprimary hydroxy group; (B) at least one unsaturated polyester resinhaving a number average molecular weight to the average number of doublebonds per polymer molecule in the range from about 200 to about 400, inan amount such that the weight ratio of polyester resin (B) topolyetherester resin (A) is in the range from about 10:90 to about90:10; (C) about 10 to about 70 wt. % of at least one vinyl monomer; and(D) at least one curing agent.
 2. The composition according to claim 1,wherein, in the aromatic polyol, Ar₁, and Ar₂ and Ar₃ when present, eachrepresent a phenylene ring.
 3. The composition according to claim 1,wherein, in the aromatic polyol, each X, when present, represents ahydrocarbylene or hydrocarbylidene group and each X′ represents a heteroatom.
 4. The composition according to claim 1, wherein, in the aromaticpolyol, h is
 0. 5. The composition according to claim 4, wherein thearomatic polyol comprises at least one primary hydroxy group and isrepresented by the formula:

wherein R₄ to R₇ each independently represent a hydrogen atom or ahydrocarbyl group, provided that at least one hydroxy group is anonprimary hydroxy group.
 6. The composition according to claim 1,wherein, in the aromatic polyol, h is
 1. 7. The composition according toclaim 6, wherein the aromatic polyol comprises at least one primaryhydroxy group and is represented by the formula:

wherein each of R₈ to R₁₃ represent a hydrogen atom or a predominantlyhydrocarbyl group, provided that at least one of R₈ and R₉ is not anhydrogen atom, X represents —(CH₃)₂—, —S— or —O—, and m and n representintegers which individually are in the range from 1 to
 5. 8. Thecomposition according to claim 7, wherein the aromatic polyol is apropylene oxide adduct of bisphenol A.
 9. The composition according toclaim 1, wherein, in the aromatic polyol, h is 1 and j is in the rangefrom 1 to
 5. 10. The composition according to claim 9, wherein X is amethylene, alkylene or alkylidene group.
 11. The composition accordingto claim 9, wherein the aromatic polyol is an alkoxylated novolac-typepolymer.
 12. The composition according to claim 9, wherein the aromaticpolyol is a propoxylated novolac-type polymer.
 13. The compositionaccording to claim 1, wherein the at least one unsaturatedpolyetherester resin comprises the reaction product of at least onepolyether and at least one ethylenically unsaturated anhydride ordicarboxylic acid wherein the anhydride or dicarboxylic acid areinserted into carbon-oxygen bonds of the polyether.
 14. The compositionaccording to claim 13, wherein the polyether is a polyether glycolhaving an average hydroxyl functionality of about 2 to about 6, ahydroxyl number of about 28 to about 260 mg KOH/g, and a number averagemolecular weight of about 400 to about 12,000.
 15. The compositionaccording to claim 1, wherein the unsaturated polyester resin (B) isderived from at least dicyclopentadiene, an unsaturated carboxylicanhydride, and a glycol.
 16. The composition according to claim 1,wherein the vinyl monomer (C) comprises styrene.
 17. The compositionaccording to claim 1, wherein the curing agent (D) comprises a catalystsystem comprising a free radical initiator and an accelerator.
 18. Thecomposition according to claim 1, further comprising at least onearomatic vinyl ester resin.
 19. The composition according to claim 18,wherein the at least one aromatic vinyl ester comprises a reactionproduct of epichlorohydrin and bisphenol A, which is further reactedwith a vinyl acid.
 20. The composition according to claim 18, whereinthe at least one aromatic vinyl ester comprises the reaction product ofepichlorohydrin with a novolac-type resin, which is further reacted witha vinyl acid.
 21. The composition according to claim 1, furthercomprising a second unsaturated polyetherester resin other than theunsaturated polyetherester resin (A).
 22. The composition according toclaim 21, wherein the second unsaturated polyetherester resin comprisesan unsaturated polyesterester resin end-capped with at least oneend-capping compound selected from the group consisting ofdicyclopentadiene, an epoxy-containing compound, and combinationsthereof.
 23. An intermediate in the form of a sheet for making a skinlaminate, the intermediate comprising reinforcing fibers and the curablethermoset resin composition of claim
 1. 24. A gel coated polymerlaminate comprising at least one fiber-reinforced polymer layer, atleast one gel coat layer, and at least one thermoset resin layerinterposed between the at least one fiber-reinforced polymer layer andthe at least one gel coat layer, wherein the at least one thermosetresin layer comprises the skin laminate intermediate of claim 23,wherein the curable thermoset resin composition is cured.
 25. The gelcoated laminate of claim 24, wherein the fiber-reinforced polymer layercomprises a reinforcing fiber and a polyester resin.
 26. The gel coatedlaminate of claim 24, wherein the ratio of the average thickness of theat least one fiber-reinforced polymer layer and the average thickness ofthe at least one thermoset resin layer is about 6:1 to about 2:1.
 27. Afiber-reinforced polymer composite comprising a cured compositioncomprising the curable thermoset resin composition of claim 1, and areinforcing fiber.
 28. A gel coated fiber-reinforced polymer comprisingthe fiber-reinforced polymer composite of claim 27 and a gel coat.
 29. Agel coated polymer laminate comprising at least one fiber-reinforcedpolymer layer, at least one gel coat layer, and at least one thermosetresin layer interposed between the at least one fiber-reinforced polymerlayer and the at least one gel coat layer, wherein the at least onethermoset resin layer comprises the curable thermoset resin compositionof claim
 1. 30. The gel coated polymer laminate of claim 29, wherein thefiber-reinforced polymer layer comprises a reinforcing fiber and apolyester resin.
 31. The gel coated polymer laminate of claim 29,wherein the ratio of the average thickness of the at least onefiber-reinforced polymer layer and the average thickness of the at leastone thermoset resin layer is about 6:1 to about 2:1.
 32. A curablethermoset resin composition, comprising: (A) at least 5 wt. % of atleast one unsaturated polyetherester resin at least partially end-cappedwith an aromatic polyol and the reaction product of at least oneacid-terminated unsaturated polyetherester resin and at least onearomatic polyol having at least one non-primary hydroxy group; the atleast one aromatic polyol represented by the formula:

wherein Ar₁, Ar₂ and Ar₃ each independently represents an aromaticgroup; R₁, R₂ and R₃ each independently represents a non-aromaticpredominantly hydrocarbyl group; each X and X′ independently representsa hydrocarbylene group, a hydrocarbylidene group, a divalent hetero atomor group, an ester linkage, or a combination thereof; each X′ can alsorepresent a covalent bond; h and k each independently represent aninteger equal to 0 or 1; j represents an integer in the range from 0 to5; and m, n, and p each independently represent an integer in the rangefrom 1 to 5, provided that at least one hydroxy group of formula (I) isa nonprimary hydroxy group; (B) at least one unsaturated polyester resinhaving a number average molecular weight to the average number of doublebonds per polymer molecule in the range from about 200 to about 400, inan amount such that the weight ratio of polyester resin (B) topolyetherester resin (A) is in the range from about 10:90 to about90:10; (C) about 10 to about 70 wt. % of at least one vinyl monomer; and(D) at least one curing agent.
 33. A method for making a curablethermoset resin composition, comprising combining: (A) at least 5 wt. %of at least one unsaturated polyetherester resin at least partiallyend-capped with an aromatic polyol, the aromatic polyol comprising atleast one non-primary hydroxy group and represented by the formula:

wherein Ar₁, Ar₂ and Ar₃ each independently represents an aromaticgroup; R₁, R₂ and R₃ each independently represents a non-aromaticpredominantly hydrocarbyl group; each X and X′ independently representsa hydrocarbylene group, a hydrocarbylidene group, a divalent heteroatomor group, an ester linkage, or a combination thereof; each X′ can alsorepresent a covalent bond; h and k each independently represent aninteger equal to 0 or 1; j represents an integer in the range from 0 to5; and m, n, and p each independently represent an integer in the rangefrom 1 to 5, provided that at least one hydroxy group of formula (I) isa nonprimary hydroxy group; (B) at least one unsaturated polyester resinhaving a number average molecular weight to the average number of doublebonds per polymer molecule in the range from about 200 to about 400, inan amount such that the weight ratio of polyester resin (B) topolyetherester resin (A) is in the range from about 10:90 to about90:10; (C) about 10 to about 70 wt. % of at least one vinyl monomer; and(D) at least one curing agent.
 34. An intermediate for making a curablethermoset resin composition comprising (A) at least 5 wt. % of at leastone unsaturated polyetherester resin at least partially end-capped withan aromatic polyol, the aromatic polyol comprising at least onenon-primary hydroxy group and represented by the formula:

wherein Ar₁, Ar₂ and Ar₃ each independently represents an aromaticgroup; R₁, R₂ and R₃ each independently represents a non-aromaticpredominantly hydrocarbyl group; each X and X′ independently representsa hydrocarbylene group, a hydrocarbylidene group, a divalent heteroatomor group, an ester linkage, or a combination thereof; each X′ can alsorepresent a covalent bond; h and k each independently represent aninteger equal to 0 or 1; j represents an integer in the range from 0 to5; and m, n, and p each independently represent an integer in the rangefrom 1 to 5, provided that at least one hydroxy group of formula (I) isa nonprimary hydroxy group; (B) at least one unsaturated polyester resinhaving a weight ratio of the number average molecular weight to theaverage number of double bonds per polymer molecule in the range fromabout 200 to about 400, in an amount such that the weight ratio ofpolyester resin (B) to polyetherester resin (A) is in the range fromabout 10:90 to about 90:10; and (C) about 20 to about 50 wt. % of atleast one vinyl monomer.
 35. The intermediate according to claim 34,further comprising a second unsaturated polyetherester resin other thanthe unsaturated polyetherester resin (A).
 36. A curable thermoset resincomposition, comprising: (A) at least 5 wt. % of at least oneunsaturated polyetherester resin at least partially end-capped with anaromatic polyol comprising at least one primary hydroxy group, thearomatic polyol represented by the formula:

wherein R₄ to R₇ each independently represent a hydrogen atom or ahydrocarbyl group, provided that at least one hydroxy group is anonprimary hydroxy group, or

wherein each of R₈ to R₁₃ represent a hydrogen atom or a predominantlyhydrocarbyl group, provided that at least one of R₈ and R₉ is not anhydrogen atom, X represents —C(CH₃)₂—, —S— or —O—, and m and n representintegers which individually are in the range from 1 to 5, or comprisesan aromatic polyol prepared by alkoxylating a novolac-type polymer; (B)at least one unsaturated polyester resin having a number averagemolecular weight to the average number of double bonds per polymermolecule in the range from about 200 to about 400, in an amount suchthat the weight ratio of polyester resin (B) to polyetherester resin (A)is in the range from about 10:90 to about 90:10; (C) about 10 to about70 wt. % of at least one vinyl monomer; and (D) at least one curingagent.
 37. The composition according to claim 36, wherein theunsaturated polyester resin (B) is derived from at leastdicyclopentadiene, an unsaturated carboxylic anhydride, and a glycol;the at least one vinyl monomer (C) comprises styrene; and the at leastone curing agent (D) comprises a catalyst system comprising a freeradical initiator and an accelerator.
 38. The composition according toclaim 36, further comprising at least one aromatic vinyl ester resin.39. An intermediate in the form of a sheet for making a skin laminatecomprising reinforcing fibers and the curable thermoset resincomposition according to claim
 36. 40. A fiber-reinforced polymercomposite comprising a cured composition comprising the curablethermoset resin composition of claim 36 with a reinforcing fiber.
 41. Agel coated fiber-reinforced polymer comprising the fiber-reinforcedpolymer composite of claim 40 and a gel coat.
 42. A method for reducingblistering of a gel coated fiber-reinforced polymer comprising: applyinga curable gel coat composition to a mold; at least partially curing thegel coat composition; applying at least one layer of at least onecurable thermoset resin composition according to claim 1 to the at leastpartially cured gel coat composition; at least partially curing thecurable thermoset resin composition; applying at least onefiber-reinforced polymer layer to the at least partially cured thermosetresin composition layer; and curing the thermoset resin compositionlayer to form the gel coated fiber-reinforced polymer.
 43. An articleproduced by the method of claim
 42. 44. A method for reducing blisteringof a gel coated fiber-reinforced polymer comprising: applying a curablegel coat composition to a mold; at least partially curing the gel coatcomposition; applying at least one layer of the skin laminateintermediate of claim 23 to the at least partially cured gel coatcomposition; at least partially curing the curable thermoset resincomposition; and applying at least one fiber-reinforced polymer layer tothe at least partially cured thermoset resin composition layer; andcuring the thermoset resin composition layer to form the gel coatedfiber-reinforced polymer.
 45. An article produced by the method of claim44.